There are many clinical studies showing the effectiveness of red light therapy for treating arthritis. In a review article on rheumatology, some 18 papers were considered. All studies involved double-blind trials with photobiomodulation in chronic rheumatoid arthritis patients and reported significant improvement in both acute small joint inflammation and chronic pain (80% success rate in relieving pain).
A different study of 170 patients with rheumatoid arthritis using photobiomodulation showed pain attenuation (pain reduction) of up to 90%. Red light therapy also accounted for increased cellular rejuvenation and blood flow, which play an important role in improving joint and tissue health in arthritic hands. Photobiomodulation also showed additional soft/connective tissue benefits like decreased oxidative damage—which degenerates joints—and decreased inflammation.
Below are quick links to some of the clinical studies that have been conducted and posted to the U.S. National Library of Medicine's National Center for Biotechnology Information:
Can osteoarthritis be treated with light? - ncbi.nlm.nih.gov
Low level laser therapy for osteoarthritis and rheumatoid arthritis: a metaanalysis.
Low-Level Light/Laser Therapy Versus Photobiomodulation Therapy
Mechanisms and applications of the anti-inflammatory effects of photobiomodulation
Low level light effects on inflammatory cytokine production by rheumatoid arthritis synoviocytes.
Effect of low-level laser therapy on the expression of inflammatory mediators and on neutrophils and macrophages in acute joint inflammation
Biphasic Dose Response in Low Level Light Therapy
A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders.
Low-level laser therapy in acute pain: a systematic review of possible mechanisms of action and clinical effects in randomized placebo-controlled trials.
The clinical efficacy of low-power laser therapy on pain and function in cervical osteoarthritis.
Improvement of pain and disability in elderly patients with degenerative osteoarthritis of the knee treated with narrow-band light therapy.